The present invention relates to an information storing device, and in particular to an information storing device having a plurality of working modes at recording/reproduction, which can be selected according to conditions of power supply for a device of higher rank, with which the information storing device is connected, and a method for driving same. The term “information storing device” used here includes a rotary type information storing device such as a magnetic disk device, an optical disk device, an opto-magnetic disk device, etc. and a magnetic tape device.
The present invention can be applied to a mounted/dismounted type and a fixed type information storing devices.
Down-sizing and diversification have been attempted also for rotary type information storing devices such as a magnetic disk device, optical disk devices, opto-magnetic disk devices, etc. and magnetic tape devices, used as external storing devices, keeping step with down-sizing of electronic computers such as so-called personal computers, office computers, work stations, etc. For example, down-sizing tendency of magnetic disk devices is such that it proceeds from 3.5″ to 2.5″, to 1.8″ and further to 1.3″. Down-sizing tendency can be seen also for optical disk devices and opto-magnetic disk devices. Hereinbelow these rotary type information storing devices are generally called simply disk devices.
On the other hand, keeping step with down-sizing of the magnetic disk devices, card type mountable/dismountable magnetic disk devices according to PCMCIA (Personal Computer Memory Card International Association) standard have been developed. For example, there are known techniques disclosed in U.S. Pat. No. 5,062,016, filed May 5, 1986, JP-A-5-181565 and further JP-A-4-356785.
As a representative specification, by which standardization is intended, including interface for electric connection, there is a recommended specification on IC memory card for personal computer promoted by Corporate Juridical Person, Japanese Electronic Industry Development Association (JEIDA), in cooperation with PCMCIA in USA. Originally it was a recommended specification exclusively directed to memory card (PCMCIA Rel. 1.0/JEIDA Ver. 4.0). Thereafter it was extended to a specification (PCMCIA Rel. 2.1/JEIDA Ver. 4.2), including magnetic disk devices, keeping step with down-sizing of the magnetic disk devices.
According to this recommended specification on IC memory card for personal computer, working conditions can be set so that a relevant memory card can be used together with other cards of an electronic computer system. According to the specification the system can be so constructed that it is prohibited to use a PC card, when working conditions offered by the PC card don't satisfy working conditions required by the system.
A parameter on power condition information is included in these working conditions. The parameter includes standard voltage of working power, minimum voltage of working power, maximum voltage of working power, current of continuous power, maximum value of mean current in 1 sec, maximum value of mean current in 10 millisec, necessary supplied current in power down mode, etc.
The system, in which use of a PC card type magnetic disk device is expected, is diversified.
That is, it extends from a work station having a sufficient power supply capacity, which demands a high speed access property from the magnetic disk device, to a portable type computer incorporating a battery, which demands low power consumption rather than access property. Therefore it is desired for the PC card type magnetic disk device used over these not specified but diversified devices of higher rank to be able to offer selectively a high speed access property or a low power consumption according to power supply capacity of a device of higher rank connected therewith.
However, as it can be seen from the recommended specification for IC memory card for personal computer published by JEIDA and PCMCIA in USA, there are no disk devices including a PC card type or a fixed type which can offer selectively a high speed access property or a low power consumption according to power supply capacity of the device of higher rank.
Personal computers of notebook size or pocket notebook size have been used more and more often outside office owing to down-sizing of computers, which has accelerated lowering of power consumption of disk devices mounted on the computers. That is, it has been tried to lower power consumption according to the tendency that smaller driving power of a disk device is more desirable. As an example thereof, there are known techniques disclosed in U.S. Pat. No. 4,933,785 (corresponding Japanese application JP-B-3-503101), in which electric power supply to circuits, for which no power is required functionally in each working mode, is suppressed by constructing a magnetic disk device so that either one of working modes can be set by classifying them into:                1) sleep mode, in which, least necessary interface function with a device of higher rank (computer system) necessary for restarting CPU being left, other circuits or function thereof are stopped;        2) idle mode, in which CPU is working and, all interface functions with the device of higher rank being left, function of a spindle motor, a servo motor, a record reproducing circuit, etc. is stopped;        3) idle mode, in which servo function is working in a state where the spindle motor is rotated and a data recording/reproducing circuit is in a stopped state; and        4) several working modes in usual operation such as a write/read mode, a seek mode, etc.        
An effect to reduce mean power consumption in the different working modes can be achieved by this method. However, by this method, no attention is paid to the initial period of the spindle motor start, at which power consumption is maximum. For this reason, no effect can be obtained to reduce specifically power current at start of the disk device.
As other prior art techniques there are those disclosed in JP-A-4-205963.
By this method, the number of turns of the spindle motor is decreased to such a degree that the rotation of the disk is maintained in a waiting mode, in which write/read is not effected. This method has an effect to reduce the transient necessary maximum power current to shorten a period of time necessary for increasing the rotation of the disk to a predetermined value.
However, in a disk device in general, frequency with which the state where write/read is not effected is produced is not necessarily so high. Further, since the state where write/read is not effected is one where power consumption is smallest next to the not working state (power consumption being 0 W) where power is not switched on (power consumption is greatest at start of the motor and next greatest at file access, in either case power consumption being greater than that required when read/write is not effected while rotating the motor), as indicated in a cited reference, even if the disk motor speed is reduced by setting a waiting mode in this state where read/write is not effected, no effect to reduce remarkably power consumption can be obtained as a whole. On the contrary, considerable power is consumed temporarily, because it is required to increase the rotation speed of the disk motor upto a predetermined value, when it proceeds from this waiting mode to a write/read operation, if the read/write state is interrupted in this waiting mode. Furthermore, since a certain period of time is required for increasing the rotation speed of the motor upto the predetermined value when it proceeds from this waiting mode to the write/read operation, this gives rise to a problem that start of the write/read operation is retarded, which lowers working speed.
In addition, in this cited reference, read/write speed is only one usual speed (one kind) and no attention is paid to setting arbitrarily diversified data read/write speeds according to needs of users.
As another prior art example, there are known techniques, by which in case where the point of time of a succeeding read/write start is previously known in a magnetic disk device, it is avoided to accelerate/decelerate the head more strongly than required to save power at seek by detecting a waiting time from seek start to read/write start and by controlling seek speed (moving speed) of the head so that the difference between this waiting time and an average seek time previously obtained for each displacement distance of the head be approximately zero, as described in JP-A-63-87663.
However no idea is disclosed to distinguish high speed seek, by which high speed processing is possible, and low speed seek effected with low noise and low power according to request of the user or according to power supply capacity of the device of higher rank. Further no attention is paid to read/write arbitrary data with different read/write speeds such as a high speed, a standard speed and a low speed according to request of the user.
As a prior art example on the high speed access property, there are known techniques, by which in order to improve operability of a reproducing device in a compact disk (CD) or a digital audio tape recorder (DAT), a second speed is automatically set for read/write of signals such as control signals TOC other than audio signals, which speed is higher than read/write speed for usual audio signals, as described e.g. in JP-A-2-156470. However, in this document, no attention is paid to record/write arbitrary data which should be used by the user with different medium speeds such as a high speed, a standard speed and a low speed or to lower power consumption according to request of the user or according to power supply capacity of the device of higher rank.
For a magnetic head used in a magnetic disk device, heretofore an inductive head is used, which produces reading voltage on the basis of the electromagnetic induction effect on winding conductor.
Recently an MR head is used, which produces reading voltage on the basis of the magneto-resistance effect. The MR head has a feature that it produces reading voltage without variations in magnetic field intensity due to relative movement of the magnetic head to a magnetic-recording face. Further for the magnetic head of hard disk drive, a floating method is usually used, utilizing a hydromechanical effect acting between the head slider and the disk surface. In addition, recently a contact method called contact recording is used, by which the head slider, on which the magnetic head is mounted, is not floated.
Requirements of users for properties of a magnetic disk device or an optical disk device can be roughly classified into two types, as described below.
{circle around (1)} high speed transfer, high speed access, and
{circle around (2)} low power consumption, low noise.
In order to satisfy the requirements defined by {circle around (1)}, it is necessary to increase the read/write speed of the disk, i.e. the rotation speed and the seek speed of the head. On the contrary, in order to satisfy the requirements defined by {circle around (2)}, it is necessary to decrease the read/write speed of the disk (rotation speed) and the seek speed of the head. These two properties are contradictory to each other and there exists heretofore no disk device satisfying these two properties at the same time, but there are different models of devices, each of which has one kind of the data read/write speed and the seek speed. For this reason every user cannot help preparing at least one model of devices satisfying each of the two properties and selecting a magnetic disk device having properties suitable for utilization conditions (whether it is used under restriction on noise level and maximum power, whether the transfer•access speed is regarded as important, etc.) for every use.
In this case problems as described below take place:                {circle around (1)} a magnetic disk device having either one of the properties should be selected, even if aimed utilization conditions are not clear;        
{circumflex over (2)} there is no way other than buying another or replacement by another, when it is desired to exchange a property of a magnetic disk device with another in the course of utilization because of change in utilization conditions; and
{circumflex over (3)} it is impossible to switch over the properties timely according to way of utilization.
Particularly such problems take place for a disk device attached to a personal computer using both a commercial AC power source and an incorporated battery power source such as e.g. a notebook type personal computer. In this kind of personal computers, since sufficient power can be supplied in case where a commercial AC power source is used, it is desirable to keep the head seek speed and the disk read/write speed satisfactorily high. On the other hand, in the case where an incorporated battery power source is used, it is desirable to lower the head seek speed and the disk read/write speed to use it at a low power consumption in order to elongate continuous utilization time of the system.
However there exist no information storing devices yet, which can be used while switching working modes of access or read/write according to utilization conditions.